1. Field of the Invention
The present invention relates to a heat exchanger and a heat exchange ventilator with a laminated structure for performing heat exchange between fluids and used mainly in the field of air conditioning.
2. Description of the Related Art
In recent years, air conditioning devices such as heaters and coolers have developed considerably and have also become more widely used, and as the living spaces using air conditioners have expanded, there has been an associated increase in awareness of the importance of heat exchangers for air conditioning devices capable of recovering heat and humidity during the ventilation process. Conventional air conditioning heat exchangers such as those disclosed in Japanese Patent Publication No. Sho 47-19990 and Japanese Patent Publication No. Sho 51-2131 are in widespread use.
All of these conventional heat exchangers employ a basic structure in which partition plates which transfer heat and are moisture permeable are separated using spacer plates, and a plurality of the layers are then superposed with a predetermined spacing between the layers. The partition plates are square flat plates, whereas the spacer plates are corrugated plates formed in either a sawtooth wave shape or a sine wave shape which in a projection plane thereof matches the partition plates.
Furthermore, each of the spacer plates is held between the adjacent partition plates so that the formation directions of the corrugations of the spacer plates alternately cross at an angle of either 90 degrees or an angle close to 90 degrees. The fluid passages of the dual system are formed so that the first air flow and the second air flow are separated, and the fluid passages running through the respective layers each comprising the spacer plate and the partition plate are formed with alternating orthogonality.
The properties required for the partition plates of a heat exchanger are a low degree of air permeability and a high level of moisture permeability. This is because in order to ensure that, during operation of the heat exchanger, heat exchange of both sensible heat and latent heat can be performed concurrently, with no mixing between the external fresh air drawn into the room from outside, and the foul air being discharged outside from inside the room, it is necessary that water vapor be able to migrate efficiently between the intake air and the exhaust air.
Examples of partition plate materials capable of coping with these demands include the gas shielding materials disclosed in Japanese Patent Publication No. Sho 58-46325. These materials are obtained by impregnating or coating a porous member with a water soluble polymer material including a halogenated lithium as a moisture absorbent. Furthermore, Japanese Patent Publication No. Sho 53-34663 discloses a method of improving the flame retardation by mixing, where necessary, a guanidine based flame retardant with the water soluble polymer material before the impregnation or coating process.
In a heat exchanger comprising partition plates constructed of the above type of moisture permeable gas shielding material formed by impregnating or coating a porous member with a water soluble polymer material, a problem arises in that under conditions of high temperature and high humidity, such as those encountered in summer, moisture absorption by the partition plates may cause a portion of the water soluble polymer material to dissolve, resulting in a blocking phenomenon and causing the material to break or tear during rewinding operations such as corrugating. Furthermore, this type of heat exchanger is produced by laminating a plurality of heat exchanger structural members together, with each structural member comprising a single faced corrugated structure obtained by corrugating and bonding the material of the spacer plate to the material of the partition plate.
The corrugation process is centered around upper and lower gear shaped corrugators which rotate and intermesh with each other and which are used for forming the spacer plate, and a press roller for pressing the partition plate material onto the spacer plate material while rotating. In order to ensure the corrugated shape of the spacer plate, the upper and lower corrugators and the press roller are normally maintained at a high temperature of at least 150° C. Consequently, a portion of the water soluble polymer material of the partition plate material tends to melt with the heat from the press roller and fuse to the press roller. Although this fusion of the partition plate material to the press roller can be prevented by lowering the temperature of the press roller, lowering the temperature can cause a collapse of the corrugated shape, making the product unusable as a heat exchanger structural member.
In order to overcome this problem, conventionally, the temperature of the press roller and the upper and lower corrugators is adjusted to a temperature at which fusion is unlikely to occur, and the feed speed is lowered to prevent any collapse of the corrugations. As a result, the productivity drops significantly, and the production costs increase. Furthermore, heat exchangers produced using a partition plate formation method which requires no chemical processing, such as those disclosed in Japanese Patent Application No. Hei 5-109005 and Japanese Patent Application No. Hei 5-337761, are also in widespread use.
In a device of the type in which two different air flows are separated by partition plates, and heat exchange of sensible heat and latent heat of these two air flows occurs through the partition plates, the partition plates are formed from a porous sheet onto one side of which is formed a composite moisture permeable film comprising a thin film of a water insoluble hydrophilic polymer which is permeable to water vapor. Consequently, there is no deformation of the device even when used in an environment which suffers repeated dew condensation, and a total enthalpy heat exchanger can be provided which suffers no deterioration in performance, even with extended use. Moreover, because the hydrophilic polymer thin film is insoluble in water, it does not mobilize and flow, and so deterioration in performance with time does not occur.
In those cases where a resin film such as that described above is used for the partition plates, a base material to which the resin is applied is necessary, and so the total thickness of the partition plate increases, and as a result, the moisture permeability of the plate decreases.
Furthermore, mixing a moisture absorbent with the resin during film formation in order to improve the moisture permeability results in unsatisfactory film formation, and attempts to impregnate or coat a completed film with a moisture absorbent do not allow the addition of the required amount of moisture absorbent.
Furthermore, another problem associated with a highly moisture permeable resin film is that it is too expensive when compared with one employing a porous base such as paper.